Electrical regulator



Sept. 29, 1931.

F. W. MERRILL ELECTRICAL REGULATOR Sept. 29, 1931. F. w. MERRILL 1,825,079

ELECTRICAL REGULATOR Filed Dec. 23, 1929 4 Sheets-Sheet 2 mmy Sept. 29, 1931. F. w. MERRILL 1,825,079

ELECTRICAL REGULATOR Filed Dec. 25, 1929 4 Sheets-Sheet 5 Sept. 29, 1931. F. w. MERRILL 1,825,079

ELECTRI CAL REGULATOR Swanton Patented Sept. 29, 1931 :Umano lsfrarri-z's .PATENT LoFl-i-cls:

-.FBANK WINTHBOB-MEBBILLgOFLFOBT WAYNE, INDIANA ELECTRICAL REGULATOR lApplication med December 23,- 1929. y Yseran 1ra-416,140.

f' This invention relates to electrical regulachemically connected to each other to .move

rasnanunit and'whcrein a solenoid isemployed for moving the .armature ,inV accordlfaneewithcircuit. conditions to vary the' immersion ofthe'resistance element in a'body w5- of vmercury! to secure the Vdesired Vregl'ilating effect I:Whilecmy prior construction referred to was found. to be satisfactory inoperation, ',thepresent construction Ahas been .developed-fas aniarked improvement there- 12o-rover in alnumber of different-respects.

An important object of the present. invenk tion fis toffprovide novel meansfor accom- AV.plishing"fthe results* referred to wherein- `a in/voltage or amperage will kautomatir-callyvfoperatefto restore in the `circuit the normal voltage or amperage conditions by -.gradua.=lly. introducino` or cutting out resist- .ianceaccording'to the type Ao `the -device `femprloyed:and:the circuitwith which it is 'muemssociated /Affurther object is to provide a regulator lofthe characterreferred to which isextrerneflyV accurate and reliable in operation, oandwhich is strong and durable and` `oper- `A`Wabrle over long periods of time Without-des Figure 4,

the sealing of the/apparatus in such a manner as to prevent the destroyingl of the accurate factoryy adjustments.

A further object-:is to rovide an instru- Ament of thecharacter re erred to which is 50 vfree fromradio interference, and which is 'fsuch character' asto provide unusual sensltivity in operation.

A-further object is to providea regulator `wherein hunting is eliminated by the senu `-sitivity and accuracy oacti-on of the moving parts, 'and which is substantially trouble :proof indefinitely.

n. A further object is to provide a regulator of such acharacter that the sensitivity and accuracy -ofzthe instrument vare preserved permanently, and wherein the instrument ir free romthexnecessity of maintenance and thehdanger. ofbeing. rendered inaccurate by tampering.

v 05 A furthercobject isto provide a regulator of such character. that the delicate and accurate .parts are protected against chemical act1on .through oxidation or through the action ofthe body lof mercury contained in the instrument.

Other objects andadvantages of the inven- .tionwill become apparent during the course of the' following description.

I-n the drawings `*I have shown Aseveral embodiments of the invention. In this showing,

i Figure 1 isy aT` front elevation,

Figure 2isa section on line'4 2 2 of Figure 1, parts being shown in elevation, 30

Figure 3 is a plan view,

.Figure 4 is an enlarged central vertical sectional view through the lower end of the instrument tube, parts being omitted and S5 j part-s being shown in section,

f Figure 5.is La-detail section ony line 5-5 of ,Figure 4,

`Figure 6 is av similar view on line--G of of different characters.

modification which will be termed a secondary regulator, y l i i Figure 12 is an enlarged central vertical sectional view oi' another modification ofthe device, and,

Figures 13 to 17 inclusive are ,diagram-y` matic views illustrating the connections of the various forms' O the deviceinY circuits Referring to Figures 1 to 8 inclusive, the numerallO designates a resistor as a'wliole which may be formed of any suitable material and which is preferably accurately inachined to provide the shape indicated in 'Figure 4. rl`he resistor, as'` will become apparent, is one of the most essential parts oi' the apparatus, and as will become apparent,

vthe resistance requiredv in the resistor may vary from an'ohm or less to several thousand ohms. |This variation is obtained by the'selection of the material from which the resistor is made, and the particular material `will be'deterininedby the use to which the apparatus is to be put.-

ih'ere are several kinds of lcommercially obtainableiesistor materials which may be used in the present apparatus, andthe materials may be purchased in the form of cylindricalrods of suitable size and specified resistance, and then may be turned down to maire a resistor of the proper shape and size. In selecting the resistor material, it is inrV portant that a material be employed which is mechanically strong and able towithstand U moderate 'temperatures 'indenitely without -be unaiected` chemicallyby the action of deterioration of its'inechanical strength or change in its specified resistance and that it mercury. Y

Intermediateits ends, the resistor is'sub- Vstantially cylindrical and then tapers Vupwardly toincreasein diameter as at 11, above which portion the resistor again tapers inwardly slightly as at-12 to decrease in diameter. yThe resistor is-provided at the upper end of the tapered portion "i2 with an outstanding slioulder 13 and as will ecome apparent, tlie 'shoulder 13 denes the vupper i' limit of the body of mercury-iii which the lower end of the resistorlis immersed when zero current 'is applied tothe device. *The resistor extends a substantial distance above the shoulder 13 and tapers outwardly -near its upper end to form an engaging face 14 for a purpose to be described.

The point 13 may be designated as the upper shoulder of the resistor, while the cylindrical portion of the latter terminates at its lower end in what may be termed the lower shoulder indicated by the numeral 15. Below the lower shoulder, the resistor is enlarged asV at 16, for a purpose to be described, and the resistor is provided withv a substantial distance beneath the enlargenientl. Adjacent itslowerrend the resistor is provided with an annular groove 18 for a. `purposeto be described. 1

.The resistor and other elements to be described are arranged within a sealed tube indicated as a whole by the numeral 19. ln several embodiments of theinvention illustrated, including the form illustrated in Figures 1 to 8, the tube 19 is illust-rated as being formed of glass, and after the device has been assembled and adjusted, the glass tube is sealed at opposite ends as indicated in Figure 2. The tube is provided near its lower end with an annular enlargement 20 receiving a coiled spring 21 constituting a resilient supporting mat for the resistor and associated elements to eliminate the danger of breakage during moving or shipment of the device. rl`lie coiled spring may -be'inserted through the top of the tube before the latteris sealed, and willexpand outwardly Vinto ythe position shown in Figure 4 when is moved downwardly to the enlargement 20.

The' resilient mattorins one 'advantageous vmeans for supporting thenioving parts in the tube 19 but it will become apparent that other resilient lsupporting means may be employed.

- The tube 19 is adapted to contain a body of inercury'22 in its lower end and it will become apparent that the resistance of' the element 10 to current passing through the body of mercury and the resistor will :depend upon the degree oi immersion ofV the latter in the mercury. As previously stated,

the normal level of theL mercury may be considered to lie at the upper shoulder 13 when no current is supplied to the device,

and in the embodiment of the invention illustrated in Figures 1 to S inclusive, the

lowest level of the niercurywith respect to the resistor, under extreme conditions, will lie approximately at the level of the shoulder 15. Y i

rPhe lower end of the tube 19 is Vclosed by a preferably tapered head 28 embedded in a block 24, preferably formed ot an insulating compound, andl this block is surrounded by a metallic ring 25. l,ein lelectricalyco'nductor l26 has one end extending through and embedded in the lower Yend of the tube 19, and the opposite end of the 5 lower portion 17 extending downwardly a Y sconductorx is ,preferablyu'weldedto the band 25. Vi'Ihe han'd25.is=surroundedfby-a metal- Ilic. coil 27 spreferablyiin, the formv of spring bronze,z and a :wire L 28 r`has .one .Y enid Welded oryotherwise seeuredrw. the Wire;271 to .form

.fa.; permanent. connection: therewith.

Referring to Figures 2 and 4,;the numerali 29- idesignates" `upper. and lower ydamping` disks-surrounding. thea-lower cylindrical. ny endl' Lof .the resistor, lthe openings in L. the 'centersV of the disks being somewhat larger sthanthe portion'ofithe resistor surrounded :therebyiin-iorderwto provide slight playbe- .tween`- the .parts 'Thisf loose connection is .15 provided in forder `'that r the disks may .be

.selfL-loeating, :and fin xorder that .any bind- A1i'ngfiaction.between the diskswandzthc tube ,Q19 mayl'beleliminatedto. provide substantially frictionless` movement of' the: parts .Within :zo the tube. The damping disks are', preferably .provided withknife edgesy 30, as shown i: in .Figure .4, .and a. displacing member 3lis arranged between the damping disks. As `Will :become apparent, `thel moving parts I of 'M5 the.devicewithinzthetube 19r are atleast partially supported :atall times by the buoy- .ancy .of the bodyl of.mercurypandtheinem- "gber'f31z is employed .todispiace an increased amount of mercury to -securey the :proper aan buoyancy. v f

. A; supportingr disky 32;;iszarranged beneath '.-the-.lofwer damping disk29 .andis-.inxturn ssupportedfhyia resilient-:wire clip 33 which --snaps into the :groovef 18 in i the lower.v end 21185 #of ithefresistor. .Therlisplacery 31 and kthe ,disk 32 loosely surroundthe lowereiidof the'resistorsoastopartake Oflimited lon- 1. gitudina-l movement to prevent :any binding 'action between e the i parts,; but "movement :of

. .45 of: thefdisplacer 3lv andA the :top of.' the disk Movement of mercury past'theedges of thedisks-29 ispermitted however, .due

*.to the fact that theiknife edges are spaced from. theV tube v119 to provide annularv spaces 50 :through which the Imercury may pass to permit upward zand .downward movement ffofthef-resiston l Ln this', connection it is f pointed: out that Nthe `.disks 29 constitute vva most fconvenient '55 -method ofadaimpingthe movement-.ofthe viresistor to prevent too frapid movement thereof, andzthusxto prevent theinertia ofY V'the-moving parts' fromv carrying the; resistor .toofar ineither direction, [By varying the diameterof thejdainping -id-isks, the areas of .the'surroundi-ng :annular spaces .may be. aariedto secure. the proper damping action.

y In fmany installationsof the apparatus for securing voltageor currei'it'regulation 5mt-.the output ofi aggeneratorv ,by vvarying the shuntr field: resistance, it is. wholly necessary :that themovement-of the resistor and asso- `ciatedv parts bel damped. YIn any given gen- =.erator a .denite length of'time is-required'to Ychangethenmagnetic flux, vand if the regulator element were permitted to .move with entire'.freedom,it would, upon any change ofload ory generator speedfaffecting thevoltage, insert-*therequired amount of resistance tozestablish the correct'field ainperepturns beforegthefield current and Vflux had time ttochangeand maintain the voltage constant. As a gresult, the over or under vol itagecondition would still exist on the regulator coil,i to be described, thus causing thev 8U pregulator'to move beyond the desired point. ySuche conditionalso would be aggravated byv the inertia of the moving parts of the device `Within the tube `19, yas Will become apparent. Asa result of-such over-correc- 1 tion, thefvoltage would be made to varyin `the opposite direction .as soon as theiield current had time to change, thus causing 'the-regulator current to reverse and move in the "other direction. Due to the same-90 cause, itwould again pass beyond the devrsired point anda condition of continued instability, 'commonlyvknoivn as hunting :would be.. established.

Inforderfto prevent hunting the move-r "ment of:` the partszxvithin the tube must be properlyresistedsothat they would move .'t-o;-.a Vrequiredxnew position no faster'than `.the naturalperiod of field flux change can follow. In this Way, overshooting is prevented andthe operation of the regulator may be. rendered stable.

.From the foregoing it `will be apparent that-the damping meansis important for its effect uponv the accuracy of the operation ofthe device, and ,aspieviously stated, the

diameterof the disks 29 vwill be determined .according to the conditions under Which the device is called upon to operate. Further- ..-more, for small `amounts of damping iti?. Wou-ld besatisfactory to use plain disks of uniform thickness. However, it has ybeen found that for greater damping a disk havying appreciable edge-thickness introduces ya fiictional resistance probably due to the vis-C75. iii cosity of the mercury,fand such frictiona-l Vresistancel seriously affects the accuracy of regulation. :It has been found that such a disadvantage can be .overcome by providing the damping diskswith lknife edges as clear-Vwl ly-shovvn in Figure.

Movementl of the resistor is. accomplished ina manner to be described by the passage of( current through a solenoid coil 34 which surrounds-the tube 19 .as shown in Figure'f' .2. The center. tube of the coil is preferably somewhatlarger than. the tube 19 and spacers 35 arearra-nged at the topand bottom of the coil-34 to properly center-,the latter-.With -respecttothe-tube 19. vfl`l.1e., spacers.35;,are fr Y preferably formed of asbestos vor other'heat insulatingv material and are spaced from each other around the'tube 19 to provide air circulation within the coil34 for cooling purposes. The ends of the coil are connected to wires 36.

The solenoid 34 is adapted to act upon an armature connected to the resistor to move `the latter vertically under changing current or voltage conditions to vary the depth-of Vimmersion of the resistor in the mercury,

I land thus vary the length of the resistance Lpath of current passing through the resistor.

Referring to Figures 2 and 4, the numeral 37 designates the armature as a whole which Y may be referred to as a plunger, and this element comprises two parts 38 and 39. `The plunger member 38 is preferably formed Vof cast iron and the member 39 of steel, for a purpose to be described. The member 39 is provided with an enlarged lower screw threaded end 40 adapted to be vengaged byV an'internally threaded collar or connecting Vmember 4l, and the lower end of the collar is provided with an internal annular shoulder 42 having an upper tapered face adapted to engage the tapered shoulder 14 of the resistor.' It will be apparent that the collar Y sistor. i 40 41 is adapted to connect the resistor tothe member 39, and the threads 40 are preferably iinely pitched so that after-the' elements have been properly tightened, no locking means is necessary to retain the parts in position, and they will not work loose over long periods of time.

The member 39 has a lower axially extending portion 43 extending into an axial opening 44 formed in the upper end of the re- |The extending portion 43 is diametrically slotted as at 45 to form a plurality of spring fingers of arcuate outer curvature, and the extension 43 is provided near its upper'end with a reduced portion 46 increasing the resiliencyy of the fingers. n

Aspreviously'stated, the resistor is made preferably of a composition having the Vproper degree of electrical resistance, and

it is desired that the resistor have perfect electrical connection with the plunger. Accordingly the interior ofthe resistor open- Ving 44 as well as the upper end of the resistor are sprayed or plated with a suitable lmetal, preferably iron, as at 47. When assembling thefelements just referred'to, the fingers 43 are preferably spread somewhat y by the insertion of a suitable implement in 'Y connection with the plunger.

the slots 45 so that when the lingers are inserted in the opening of the resistor, they will have rm engagement with the metallic plating` 47 to form an intimate electrical This electrical connection is rendered still more perfect by the engagement of the lower end of the plunger with the plated or sprayed surface on the upper end of the resistor, and

also byv virtue'of the` clamping actionA of the collar 41 `against the shoulderr14 of the resistor. Accordingly no resistance enters into the circuit through the resistor except` the ren sistance of this element itself, andaccordingly the desired .resistance may accurately be obtained. Y. i

Above the threaded portion 40, the member 39 is provided with-an outstanding bearing collar 48 having its upper face preferably slightly tapered. Th'e bearing collar is provided `with a pluralityy o f` peripheral notches 49 as clearly shown in Figures 4 and 7. In this connection it Vwill be noted that during handling and shipment of the device, the mercury often finds its way into the upper end of the tube, and lupon ithe placing of the tube in normal position, the

mercurycan flow into the bottom of the tube through the notchesl 49. Y

The member 38 ofthe plunger is tapered to decrease in. diameter toward its upper end kand is provided in its lower end with a threaded opening 50Y receiving a threaded axial stem 51 formed integral with the member 39. The threads of the'member 51 also are finely pitched'to eliminate any p0ssibil ity of the members 38 and 39 becoming Vloosened or disconnected from Aeach other.

rlhe plunger member'38 is preferably formed of cast viron as previously'stated, although under some conditions the plunger may be made of an integral piece of steel. If the present device were to be used only in direct current Vcircuits the entire plunger could be Viron and cold rolled steel respectively.

The design Aand arrangement of the parts described within the tube 19have been found to play an important part in the operation of the device where great accuracy is desired. For example, itis found thatexcellent results can be obtained with resistors and plungers designed and proportioned substantially as shown in Figure 2 with the upper end ofthe 'plunger projecting through the coil 34 a distance equal to one-quarter of the length of the'coil. As previously '100 made in one piece and soft steel or rod iron n stated, the level of the mercury preferably is arranged at the level indicated in Figure 4 when the resistor is inits normal or d downward position and when the resistor is moved upwardly through its entire range of ntf a pigtail 59 is electrically connected to the movement, the level of the mercury will lie substantially in the plane of the lower shoulder l5. The apparatus is so designed that the length of movement of the resistor and the elements connected thereto is equal to 4() per cent. of the length of the coil 34. Extreme accuracy can be secured under the conditions described, and this degree of accuracy is increased by other factors to be referred to later.

At its upper end the plunger is connected to a conductor rod 52 preferably'formed of copper and plated with iron to resist the action of the mercury when in contact with the rod 52.l Copper is preferably employed in making the rod 52 for the reason that it is an excellent vconductorof electricity and is non-magnetic and it has been found that the plating of iron serves to protect the rod from the mercury, but does not magnetically affect the action of .the coil 34 upon the plunger. Referring to Figure 8, it will be noted that the rod 52 is provided with a dependingaxial stem 53 threaded in the upper end of the plunger member 38, and the contacting ends ofy the Vplunger and rod are preferably tapered as at 54 and machined whereby a perfect fit is obtained to prevent the entrance of mercury between the members referred to, and thus any chemical action whichthe mercury might have on the lower end of the stem 52 is prevented.

yAt ,its upper end, the rod 52 isprovided with ak bearing washer 55 above which is secured a cup-shaped bumper 56 having spaced upstanding fingers 57. The slots between the fingers 57 ,extend into the base 56 of the cup, and the bearing washer 55 is also slotted as shown in Figure 2. The elements 55 and 56 are riveted or welded` to each other to retain the slots of these members in registration so that any mercury which ndsits -wayinto the upper end of the tube 19 may :tlowk downwardlythrough theV slots referred to lwhen the device is placed in operative position.

The bearing washer 55 and bumper 56 are secured in position on the upper end of the stem 52 by a screw 58, and the lower end of rod 52 by the screw 58. Theepigtail should be highly flexible and in order that accurate results may be obtained it is preferred that the mechanical resistance of the pigtail be retained at less than 1 per cent. of the` net weight of the moving parts within the tube. The pigtail is preferably made on an iron plated copper ribbon although a number of strands of fineiron wire may be employed in special cases.

The stem or rod 52 serves as electrical connecting means between the plunger and the pigtail 59, and it also serves to place the pigtail and the steel bearing washer 55 and steel bumper 56 at such afheight above the coil that these elements will not magnetically affeet the operation of the coil.

The upper end of the'tube 19 is closed as at`60 and is embedded in a block 61 formed of an insulating composition. VVThis block is surrounded by a metallic band 62,- which in turn, is surrounded by a coiled wire 63 preferably formed of silver plated spring bronze to afford a perfect electrical connection with the band 62. A conducting wire 64 has one end preferably welded to the wire 63. The block 61 and metallic band 62 are similar t0 the corresponding parts of an incandescent lamp base, and. in fact some o f the smaller regulator tubes are fitted at either end with standard automobile headlight bulb bases.

The construction of the elements within the tube and the materials from which such elements preferably are made have been previously described, and it will be apparent that some of the elements are formedl of copper and others of iron for electrical reasons. Where copper is employed the parts are preferably plated with iron to resist the chemical action of mercury, but it will be apparent that the iron ris subject to oxidation which, after the device has been in operation for a long period of time, could affect the accuracy of the device. The operating parts are arranged inthe sealed glass tube 19, and thus they are protected from outside influences of all kinds. It is impossible for any air to reach the interior of the tube and it is likewise impossible for anyone to tamper with the operating parts of the device, and in order that-.the parts may be protected Afrom oxidation, the tube 19, prior to being sealed is preferably completely filled with an inert gas such as nitrogen. Accordingly after the tube is sealed it forms complete protection for the sensitive working parts of the apparatus, and these parts are adapted to remain indelinitely in the condition which they are originally placed within the tube.

In my prior patent above referred to la radiating element is disclosed for dissipating the heat generated in the device. No radiating element has been disclosed in the present application since it is not necessary to use such adevice in many cases. In special cases, however, where a large amount of heat energy must be dissipated, it may be necessary to employ a radiator, and any suitable type of radiator may be employed.

Any suitable means may be provided for supporting andl protecting the elements previously described, and one forni of supporting means has been illustrated in Figures 1,

2 and 3. Such a device is adapted to properly house andprotect the tube 19 and associated parts and is also adapted to permit the free access of air to the parts to be cooled.

Referringto Figures 1, 2 and 3, thenumerall65 designates'an upper housing member having a -iiange 66 at its lower end adapted to seat against the top of the coil 84C. K- The member 65 is provided with a plurality :of air circulation openings 67 as clearly shown.V v f VA Vsimilar housing member 68 receives the .lower end' of the tube y1.9 and is provided 'at its upperend with Va flange 69 seating against theV bottom of the coil 311. rlhey lower housing member also is provided with a plurality of circulating openings770 and these openings in conjunction with the openings of the upper housing member permit aV free circulation of air around the tube 19 as will be obvious. v

The two housing members are clamped in position by means of bolts 71 passing through the flanges 66. and 69. rlhe lowerV housing member is provided with a pair of Voffset bracket members 72 by mea-ns of which the devicefmay be attached to a vertical supporting surface. Between the attachingrflanges, the lower housing member is provided with a transverse member 7 3 carrying a pair of clamping Vplates 74 c onnected thereto by screws 75. The clamping plates are adaptedto receive the wires 28,

36' and V64: therebetween, and Vto be firmly Y klowerlend surrounding the upper end of the Y insulating block 61 and the upper end of the spring is seated 'withinthe upper end of the housing member 65. v

A screw 77 is threaded into vthe bottom of the lower housing member 68 in axial alinement .with the tube 19 and is provided at its upper end with a cupped disk 78 to support the bottom of the tube. Any suitable material may be arranged within the cup 78, and in practice'it is preferred to employ a layer of felt Y7 9 having a thin metallic disk Soarranged thereon i to vdirectly support the insulating block 24 (seeligure 4). As previously'stated, the distance which the upper end of the plunger projects upwardly through `the coil 3A when the parts are in lowermost position is important to the accuracy of the instrument, and adjustment ofthe plunger 37 may be secured by proper operation of" the screw V7 7. This element constitutes Athe only adjustable part of the apparatus.. The bottom of the lower supporting member is split at one side as at 81,

and ua clamping screw '82 isA o'perable for clamping'. the screw 77 been adjusted.

The `form of the device described above may be considered as a cpositive regulator, the minimumv resistance. to the "circuit through the elements within vthe tube 19 bevingbflered whenV no current is passing through the coil 34. `Under the conditions stated, the resistor will be arranged in its lower position with a minimum body ofiresister material disposed between the .plunger the surface of the niercury,and the relatively thin intervening Vwalls of resistor material.

after the latter' has i VIn Figure 9 of the drawings a negative i' type of regulator is illustrated wherein maximum resistance, rather than minimum resistance is offered when no current is passing through the regulator coil.` Inasmuch as a number of the parts of the negative type referred to are'identical with'those of the positive type, the parts of the negative type will not be described in detail. A similar tube element Vmay be employed as in the preceding case, although longer, and the electrical connect-ions are the same as will be apparent. In this case, a resistor 83 is em-k ployed which is somewhat similar to the resistor previously'described. The resistor 83 is provided at a point spaced from the upperend thereof with Va portion 84 tapered to decrease in diameter toward its-lower end, and below this tapered Yportion a second ta'- peredportion 85 is provided which decreases Y indiametertoward its lower end to the point 86 which constitutes the low point of the level of the mercury 22 with respect to theV resistor when no currentis flowing through the regulator coil 34 surrounding the tube 19 of the'negative regulator. Y

The resistor is enlarged below thefpoint 86v as at 87, and the lower end88 of Vtheresistor is substantially cylindrical'in cross sectiony to receive Va displacing member 89.

As will become` apparent, the upward force of the displaced mercury must be greater than the net weight of the parts movable in the tube of the negative type regulator when zero current is passing lthrough the coil. Accordingly the displacer 89 is `materially larger than the displacer 81A whereby the buoyancy of the mercury is adapted to over balance the weight of the parts in the position shown in Figure9 when no current is flowing through vthe coil 311.Y The movement due to the upward thrust of displacer 89 is ch'ecledthe fingers-of'cup 106 comino' in34 for substantially one-quarter off thecontact with the converging slope of-tu e 19latits upper' end. l As inthe preceding case, dampingwashcrs 90 and 91 surround the shank 88 above and below the displacer 89, these damping washers"being'provided for the purpose previously described. lVhile in each case the l dampingfwashers have been shown as being 'y arranged at oppositer ends of the displacer, suchI construction is provided as a matter of convenience-andl eiiiciency, and it will be apparent that the invention is in no way limit- Y, ed to the relationship between the damping disks and the displacing element. The parts justfdescr'ibed are' supported with respect to the=resistr^by means of a lower washer 92- and Tafresilient ring 93 engaging in a Vgroove l n in-thelower`end of the resistor, and operating -'in a-'manner similar to the spring clipY 33 previously described. l

Aicoupling member 94 is arranged at'the upperI end'V of Tvthe-resistor and is provided l with a depending portion 95, preferably 28 identical in construction with the lower end of the plunger 39 illustrated in Figure-4, the coupling member being provided with spring prongs or fingers adapted to engage the sprayed lmetallicA coating in the opening 96 formed yin the upper end of the resistor. At its"upper end, the coupling 94 is provided Withan-l outstanding guide flange 97 which is sltted for the same purpose as the guide flan' e 48 illustrated in Figure 4.

3f T eupper endof the resistor isprovided with: an outstanding annular flange 98 adaptedt be engaged by the lowerflange of 'a coupling sleeve 99 which has threaded engagement with lthe body of the member 94, and it will belapparentthat the threads connectin'g the members 94 and 99 may be finely pitch'edto eliminate the necessity for any locking means between the parts referred to. In'thenegative type of 'regulator7 a conducting rod 100 is threaded at its lower end as Aat 101 withinan openingformed in the couplingmember 94, and accordingly this member` serves to couple fthe resistor to the vi'ou'sly described, except that it is inverted whereby-fit decreases 4in diameter toward its lowerend.- The lower extremity of' the "W plunger 103 extends into the top of the coil rod 100'1 both` electrically and mechanically.

length of the coil.l Near its upper 'end,the plunger is provided with a -cylindrical portion 104 above which is larranged an outstandingfguide fiange 105 similar in iconstruction and purpose-to the flange 97.

A bumper 106 is secured against vth'e'up'per end of the plunger by a screw 107, the bumperbeing similar in construction to the bumper 56 previously described and including' spaced spring arms between which any mercury in the upper end ofthe tube may flow' downwardly when the devicel is arranged infl operative position.y The screw 107 also serves to connect'to the plunger one end of a pigtail 108, as clearly shown inl Figure 9; The parts at the upper extremity of the tube* are substantially the same as inthe type previously described and-need notbe referred to in detail.

In the form of the invention 'shown in Figure- 9, it will `be apparent that the resistor 83 will introduce a maximum 'amount of resistance in the circuit when no current is passing through the coil, and increased current-in the coilwill attract the plunger 103 to move it downwardly and thus'further immerse the resistor in the body of mercury to decrease the resistance in the cir-` cuit. The negativetype of regulator described has certain advantages. For eX- ample, it can be used directly inthe field circuit of-a counter E. M. F. motor which may Vhave its armature circuit connected in` series with the shunt fieldv of a large' generator, or in series with a loadl for thev purpose of regulating the voltage of theA generator or of the loadfor varying external conditions by vlthe insertion ofv a varying counter E. M. F. in these circuits.

It will be apparent that the device illustrated in Figure 9 emhodiesthe same struc'-I tural characteristics as the form of ther invention previously described, the 'plunger' being preferably-formed of iron and the-rod 100 of copper plated with iron, etc., and the' tube of course, is'also filled with an' inert gas such as nitrogen to eliminate oxidation of the-parts.

In Figure 10 ofthe drawings a positive' regulator is illustrated which is similar to the form of the invention shown in Figures 1 to 8 inclusive, the principal difference being that a metal tube is employed in place of a glass tube. Referring to Figure 10 they numeral 109 designates a seamless metal' tube surrounded by the usual regulating coil 34. The metal tube is preferably formed of steel tubing, but it may be made of copper plated on the inside with iron. It is entirely possible to employ steeltubing whichV has a tendency to shield the plunger from the coil flux, but laboratory tests `have shown that whenV ther coil ampere turns lare' increasedapproximately 25`v per f cent. overv 3 sion 119 carried by the latter, and a guide thevalue normally used with afglass tube regulator, the steel tubebeoomes saturated and olilers no further interference with the action ofthe device. kThe characteristic regulating curve is just asV accurate-as that 'of the regulatorsV utilizing` tubes or" non- ,inagnetic material. Y

, A plunger 110'is mounted within the tube Aandjis similar in construction and operation` to the plungers previously described exceptthat it isprovided with guide means in the form of diainetiically extending pins 111 formed of insulating material and of aV length slightly less than the internal di- Vameter ot the tubelOQ sov as not to bind thereagainst. The plunger is connected at itsV lower end bya coupling 112 with the resistorV 118, and the latter is provided at its lower end with the usual damping disks 114 and displacer 115. In placel of the resilient mat previously described for supporting the lower end of the moving parts within the tube, a coil spring 116 is employed and rests upon a steel block 117 mounted in the lower end of the tube.

llhev upper end of the plunger is connected to a conductor rod 118 by a threaded eXtenineniber 120 is arranged between disks 121 engaged by the adjacent end faces of the plunger and conducting rod. The guide member V120 isprovided with milled slotsto 'permit mercuryp-toilow therethrough, and. the member is madeoi'` insulating material, as will be apparent., j Y

`The upper end ofY the rod 118 is provided l with a pumper 122 for the same purpose as serve sto attach the lower end of a pigtail' 'preiierably in the form of sheetmica.

mica cap 126 also is arranged over the end.

the bumpers previously' described and connected to the upper end ot' the conducting rod 118 byv a screw 123. This screw also 124ito the upper end of the rod 118. Y

'A In order to prevent electrical contact be.- tween the lingers of the bumper 122 and the metallic tube 109, the upper end of the latter is lined with insulating material' 125, A

viously described 'and also is lled withA nitrogen or any other inertlgas.

All of the regulators described above are what may be known as primary regulators, that is, they are so constructed as to operate on an accurate'lifting curve Vwhich causes the plunger to float anywhere in its stroke with the same vcurrent flowing in the coil. regulate either voltageor current by sup plying the coil 34 with a suitable winding.

Because of their operation on such an ac#l curate lifting curve they may be classified previously as primary regulators Vas stated, it being apparent that they are acf curate inV themselves and capable of transmitting this accuracy to any circuit with which they may be connected. In other words, they. are master regulatorswhich byV their yown characteristics directly control the voltage or current` oi' `the generatoror of the load to which they are connected.

Sucha regulator also may be considered to` This being true, they can be made toV be an automatic iheostat which makes possible a smooth change in resistance without steps, and also provides practically frictionless bearings in which this resistance can.V move,togetherwith means for damping the movement of the parts.

The construction of a primary regulator requires great care. The resistor and plunger must be carefully machined, thel mercury' level must be accurately adjusted, the head of the plunger must normally project the proper distance into the coil, the mechanical resistance ofthe pigtail must be kept at less than 1 per cent. of the minimum'net vweight of the parts andthe coil must not be allowed to heat more than approximately 5 per cent.

or tliej regulating accuracy will be spoiled. The degree of accuracy in the making and adjustingfof the parts places the primary regulator in the class of a precision instrument, and contributes to a large eXtenttoV the cost of manufacturing the instrument.

A valuable secondary regulator maybe provided however if sacrifice ismade'in accuracy. kSuch a secondaryd device retains the unique propertiesof the automatic frictionless Vrheostat mentioned above and pos sesses still another valuable property, that is, itsv power amplifier characteristic, consideredv as a resistance., For example, the

Yprimary regulator Vpreviously described requires only 3 vwatts of energy expended-1in the coilv34 to float the working parts within the tube. The resistor on the other hand can dissipate about 30 watts of energ or a ratio` of 10 to 1. If a device employing the same size parts didjnot have to be employedA as a master regulator with an accuratecurve, the energy of the resistor could be doubledV giving a ratio of 2O to 1. The cost of`manufacture also would be lessened by the elim-y ination o f the accurate assembling and testing lrequirements and by the elimination of` a large part of thel machine worknon the resistor. j

iie

v The lifting curve in such av secondary regulator would not be completely spoiled, but would be rendered approximately -15 per cent. inaccurate. If the coil energy were increased in the small secondary regulator previously described, from an initial value of 3 watts toa final'value of 4 watts by an external regulator, the resistor could be lifted its full stroke. Thus an expenditure of 1 watt in .an external regulating device connected in the coil circuit of the small secondary regulator would enable 6() watts tobe controlled, thus giving a power amplif ingratio of 60 to 1. In like manner, if t e 30k `'watt primary regulator were fully loadedby the coil current variation of a correspondingly large secondary unit, the two units 4would be able to control 1800 watts. This obviously is a very valuable property entirely independent of the regulator characteristics. It is brought about by the small amount of energy required to move even a large resistor when it is `balanced and oatedvertically' in -a' liquid and vguided on nearly frictionless bearings.

At this point attention is invited to the lfact that the -smaller end of the armature plunger, when in Ynormal position, extends a comparatively short distance. into the axial opening of the regulator coil winding. It has been found by experience that satisfactory `results are obtainable by having the plunger extend substantially through onequarter ofthe length of the coil winding. By such arrangement the beginning of the working stroke of the plunger is below the uniform pull Zone of the solenoid Winding. Accordingly as the plunger moves upwardly, inthe case of the positive regulators, the pull of the solenoid winding rapidly increases and then gradually becomes more nearly conjstant as the plunger approaches or reaches the uniform pull zone of the coil winding.

This increase of the pull of the coil winding upon theplunger as the stroke progresses is also-partly due to the tapered shape of the latter.

. The purpose oftaperingthe plunger to increase in diameter toward its'lower end,

in the case of the positivel regulator, is to provide meanswhereby'the pull or lifting Yforce of the coil winding will increase as the `plunger r1ses.

It will be apparent that upon upward movement of the resistor, the buoyant force of the mercury thereon decreases.

In this connectiony it lwill be noted that there are three vertical forces acting on the instrument, namely (1) the weight Aof the Aplunger and resistorfand the elements connected thereto acting downwardly, (2) the 'magnetic pull of the solenoid winding actvingjvupwardly upon the plunger'with increasing force according to thel degree of taper of the plunger and the extent to which theplunger has entered the solenoid winding, and the buoyant force of the displaced mercury acting upwardly upon the resistor with decreasing force as the stroke proceeds. It is desired tnat for all positions of the parts, the force (l) be balanced at all times by the sum of the forces (2) and which result is accomplished by the predetermined shapes of the plunger and resister and the starting position of the plunger `with respect tothe coil winding. Such a construction provides a nne balance b means of which the solenoid winding wil move the plunger upwardly upon a very slight increase in current passing therethrough.

n As stated above the invention is capable of application as a secondary regulator for the purpose described,4and such a regulator is illustrated in Figure 11 of the drawings.

eferring to this figure, the numeral 131 designates a glass tube similar in construction to the corresponding element previously described, but somewhat shorter due to the elimination of parts to be referred to. The insulating and electrical connections at the ends of the tube may be the same as those previously described and need not be referred to in detail. The secondary regulater employs a resistor 132 which may be of uniform diameter in view of the fact that extreme accuracy is not required. The damping disks, dispiacer and resilient supporting mat associated with the resistor need not be described since they correspond to the similarelements in the form of the invention lillustrated in Figures l to 8.

as shown in Figure 11. In this form of the invention, the conducting rod at the upper end of the plunger is eliminated in order to simplify the construction and to shorten the glass tube, and the parts 135 and 136 may be made of spring steel and iron as in the Aprevious case even though they are arranged within the regulator coil, since extreme accuracy is not necessary as previously explained. The elimination of the conductor rod diminishes the weight of the floating parts, however', and accordingly the dis- Vplacer is made correspondingly smaller.

A further modiication of the invention, primarily intended as a secondary regulator, is illustrated in Figure 12 of the draw VReferring to this gure the numeral 138 designates a glass tube in which is arranged a resistor 139, preferably of relatively large size for use in a high-watt ca- .5

pacity secondary regulator. The resistor is Vprovided with an axial opening 140 cored entirely therethrough. The resistor is preferably cylindrical substantially throughout and displacer 143. A coiled spring 144 isy its active'length, and is reduced at its lower end as at 141 to'receive damping disks 142 snapped over the lower end of the resistor and forms a resilient support for the moving parts.' 'j At its upper endfthe resistor is taperedto increase slightly in diameter as at 145, above the level of the mercury 146. The tapered g Vportion of the resistorand the Vupper extremity thereof are preferably metal plated 2o as at 147. This metal coatingmay be either iron or copper, and if the latter is'employed it is preferred that the mercury be prevented from coming in Contact therewith. The numeral 148 designates the plunger which is provided adjacent -its lower end with a guide ange 149 having peripheral slots as in the cases of the guide anges previously described. The resistor and plunger are lcon- .nected together by` a clamping sleeve threaded on the lower end of the plunger and havingy an internal tapered lower portion adapted to engage against the metal plating of the tapered portion of the resistor. Adjacent its lower extremity the clamping sleeve is internally grooved as at 151 to prevent cutting into the tapered portion of the- -resistor when the clamping member is tightened in position. The internal diameter of the clamp below the groove 151 is preferably equal-to the diameter of the body of the resistor if copper plating 147 is employed, to

protect such plating from the action of the mercury.

A spring washer 152 is interposed between the adjacent ends of the resistor and plunger to produce a strong reactive force always tending to keep the tapered surfaces of theV resistorand clamping sleevetight, the spring washer taking up any movement'occurring through expansion differences in the materials' of the plunger and resistor.

The lower end of the plunger is provided ywith'an axial coredopening 153 communieating with the opening 140 of the resistor,

and radial Vopenings 154 communicate between the opening 153 and the interior of `the tube 138. Accordingly it will be apparent that'the mercury within the opening 140 @will always assume the same vlevel as the mercury surrounding the resistor.

The several forms of devices described are adapted for a variety of uses, and several ofk the uses have been diagrammatically illustrated in Figures 13 to 17 inclusive. In Figure 13 there is illustrated'aself-excited shunt'type D.' C. generator having a secondary positive regulator indicated Aby they numeral155 arranged with its resistor 156connected in series with the shunt field 157.

The regulator coil 158 is connected across thebrushes of the generator in the manner shown. The numeral 159 designates a pri- Y mary negative regulator the resistor 160 of which is connected in series with the coil 158, Vwhile the regulatorcoil 161 of the regulator 159 is connected acrosstlie brushes of Vthe vgenerator through a variable'resistance 162. The secondary positive regulator may be of the type illustrated in Figure 11 while the rimar negative regulatormaV be of the type illustrated in Figure 9. The

regulator 155 is wound with a single coil which must bel actuated so as to accurately adjust the-field resistance in case the -gen- Y erator field tends to vary. This resultl is yaccomplished by the insertion of the primary Y negative regulator 159 in the circuit of the regulator 155.- Y

Under normal conditions, when the gen-V erator is at rest, the secondary regulator resistance is at a minimum, and the generator builds up its voltage easily under full field conditions. Thisrise in k'voltage has no lifting effect on the field resistance 156 because the maximum resistance of the primary negative regulator 159l is in series with the coil of the secondary regulator;

The voltage therefore continuesto riseV until it reaches the p oint for. which the primary regulator coil 161 has been'set by the resistance 162. The moving element of the primary regulator then moves downwardly .cutting out resistanceV progressively until'the resistor 156 vof the secondary regulator lhas lifted'far enough to maintain constant voltage. VThis arrangement has the advantage, as already ypointed out, that a very small primary regulator can by means of the energy amplifying property of the'secondary regulator control a large generator.

In Figure-14 of the drawings Aa system is illustrated whereby a primary positive Vregulatorof the type, Vfor example, Villus-v trated in Figures 1 to 8 inclusive, may be made to actuate a secondaryV Vpositive regulator'of the general type illustrated in yFigure 11 for controlling the generator shunt Vfield current by winding the secondary regulator with two coils differently connected. l

In this case, the secondary regulator, indibem-,ore

the'brushes of thegenerator in series with a variable resistance 171,

rPhe coil 166 may be termed the main coil and lthe coil 167 the differential coil of the regulator 163. Both of these coils yare obviously excited 'from the same source,

'but the'differential coil, as illustrated, is ar` ran ed in series with the resistor 168, Ac-

cor ingly the main coil 166 is the stronger '10 'of the two and supplies the flux for lifting the resistor 164 of the secondary regulator :163. However, when the voltage is below the :regulating point for which the primary Y regulator 169 is -set by the .resistance 171, resittance is reduced in the circuit of the .dif-

ferenti al' `coil 167 by downward :movementof fthe-resistor 168 into lits associated body of 'me'rcur` and accordingly the differential #coil 1 will be strengthened so greatly as 2nite counteract the action of the main coil 166to prevent the ilifting of the secondary resistor '164.

When the eld has reached .the point for which the primary regulator is set, this device acts promptly, increasing the resistance 4in the circuit of the coi-l 167 by lifting the resistor y168, thus weakening the differential coil 167 su'liciently to permit the main field 'uxlof the coil-166 to liftthe secondary re- Losi'stor 164. Accordingly it will be apparent .that ythe results accomplished in the systems illustrated in Figures 6 and 7 are prefeisely Athe same, tbut the types `of regulators em loyed are different.

1. @hesecondary displacement regulator, beeauseof its power amplifying characteristic, lbecomes 1a ,valuable device in connection `with Athe speed regulation of motors. It furnishes a means-of multiplying the comparatively feeble energy which can be safe- 'ly carried by the contacts of a vibrating centrifugal.speed'regulator to a point that l'will enable such a vibrator to easily control `a every large motor; or in the case of small :motors Vthe vuse of the secondaryY regulator feo greatly reduces the energy to be-carried by the contact points of the speed regulator as to greatly increase the life of these 'conv Figure y15 shows a shunt wound D. C.

fniotorconnected so asto have its speed reg- 'nlated lby '1a centrifugal speed regulator in combination with a secondary negative displacementfregulator illustrated as a whole,

*51176 and 177'-v and a suitable resistance 180.

Yening the ymotor shunt field and preventing Vthese contacts into engagement 1n opposi- The resistor 173 lis connected in series with .the shunt field coil 181 of the motor.

When the motor speed reaches the poi-nt for which thefspring 178 has been set, the contacts 176 and 177 close and vibrate rapidly across the resistance 180, strengthening the current of the regulator coil 174 vand `moving its resistor 173 downwardly into the Vbody of mercury associated therewith, thus reducing the resistance of and strengthf a further rise in speed. It will 'be apparent that if the speed regulator were reversed iin type whereby its contacts were normally closed by a spring and lopened by centrif- ,w ugal force, Vthe regulation of the motor still could be accomplished by employing a displacement regulator of the positive rather than the negative type.

Figure 16 of the drawings illustrates a series Wound motor having its speed regulated by a secondary positive regulator in combination with a centrifugal speed regu lator. Referring to Figure 16, the numeral 182 designates a secondary positive displace- Vment type regulator as a whole including .a resistor 183 and a regulator coil 184, the former being connected in series 'with the series field coil 185.

A centrifugal speed regulator of the type illustrated in Figure 15 is employed including an arm 186 carrying a contact 187 adapted for engagement with a stationary contact 188, a Weight 189 tending to move vmo tion to a spring 190. A resistance 191 is connected across the contacts as shown. Increased motor speeds will operate the v1- bratmg regulator, 1ncreas1ng the res1stance of the element 183 and reducing the volt- N5 lage applied to the field coil and armature of the series motor, 'thus controlling fthe speed of the motor.

It is also evident, from the arrangement shown in Figures 13 and 14 for secondaryyw voltage regulation, that if it were desired to use a type of centrifugal speed regulator having its contacts normally held closed by a spring and adapted to be opened by centri ugal force, for the control of a series motor and still retain the secondary positive regulator, this could be accomplished `.by providing the secondary regulator 192 with a main coil 193 and a differential coil 194, and connecting the centrifugal speed regulator as illustrated in Figure 17. A regulator of such type would include an arm 195 having a spring 196 tending te maintain contacts 197 and 198 Ain engagement with each other, and opposed by a 'it weight 199. The contacts of the speed regulator would be connected in shunt with a resistance 200 connected in series with the differential coil '194.

It `will be apparent from the foregoingo that the operating characteristics of a secondary displacement regulator of the type described may be reversed either byv change of its internal construction from positive to' negative, as Lsuggested in Figure- 9 of the drawings, or by winding its solenoid with twoV coils,`and byconnecting the source of primary regulation, whatever.l it may be, so

vas 'to control "the strength of the differential coil, te oppose the action of the main coil.

The operation ofgthe'variousV forms of the invention will be apparent from theV foregoing description, all of the various typesof displacement regulators disclosed embodying Vlargely the same advantages. "Eachof the devices has its sensitive operating elementsV arranged in a vpermanently Y `sealed tamper-proof vcasing and, arranged in an atmosphere of an inert gas such as nitrogen and thereby protected ,from dirt, moisture, oxygen, etc. Portions of the device,

` such as the conducting rod 52 of the form by. means zof the screw 77, illustrated in Figure 2, whereby/the smaller end of the plunger may be properly arranged with respect to the regulator coil or solenoid This adjustment is onlyV provided to enable the Ii'actory-totake care of unavoidable manufacturing variations in the length of the glass tube and shouldnever have to be used after the regulator has been placed in service. ll, of the remainingel'ements of the device are assembled and adjusted at the j'factory, and suchadjustment obviously is f permanent.

In view of the fact that the elements" are sealed and permanently protected, it will be The deviceV as constructee is ida ted 'to` Y L c p Vsorted,to-.without departing ifrom thespirit of the invention-or the scopeJofthe subf apparent that the device is wholly trouble- Mproof and requires no attention Whatever in. operation. The apparatusV also is :relatively inexpensive and is highly convenient in operation. 1 v

operate juiider minimum variations of temperature'conditions which do not aect its accuracy, and it is usually unnecessary to v`provide any cooling means.` ril`he damping means employed in the form of thedainping disks ei'ectually prevents overrunning of the jrection without materially introducing fricltion,fand. without materiallyl affecting its ployed according to the particular installa,- tion. i

' The use of the disp'lacer 115 operates `to Y adjust the Y buoyant Vefectvof the mercury with respect tothe Vmoving partsvvhereby a portion of ythe weight of the parts will be permanently ibalanced. The accuracy of operation of the device'is possible largely Vbecause the increased pull ofthe regulator coil with tliesame current Howingbalances v the progressively decreasing'buoyancyofthe mercury `as the parts-move upwardly, as

accuracy of the instrument.A

Attention also is invited to the that the device causes a smooth change of resistance in its circuit without steps, and with-l out the use of vibrating contacts andthe consequent sparking thereof. lt 4also will be apparent that the movementfof the parts is substantially frictionless and `Without wear, thus permitting the device 'to be em-A ployed indefinitely Without any changeV in its accuracy.

As compaieclwvitlimyprior Patent No. 1i,220,255, previouslyreferredto, the present invention permits the vuse Aof a-single glass or other tube in place of the 'bi-metallic tube employed in the prior. patenty referred to. Thev sealed jointsV employed in my prior vmovement lof the resistor in each form of patent toexcludeair, oxygen or moisture also are eliminatedfby the use of a. sealed glass tube illedfwitli dryinertA gas.- The restricted opening in the bottom-of the resistorfin'my prior'patent-to damp the-iow of mercury alsois eliminated and improved upon by the employment of thejdamping disks, and the conical portion of the resistor at the upper end of the opening therein also iseliminated. Y' lt is to be understood that the forms of the invention herewith shown and described are to be takenas preferred examplesof the same and that various changes in the shapes, size and arrangement of partsmay be-rejoined claims. f A i y l claim@ e' t l. Apparatus comprising a substantially vertical tube, a

i A bodyvof a,liquidelectrical conductor conmoving parts within the tubein either di,

tained insaid tube, a'resistor arranged in said tube and projecting downwardly into saidconductor, electro-magnetic means for varying the depth of `the immersion 'of said j resistorjin said conductor, means carriedby of the character described' iio said' resistor below the level of said conductor for increasing the buoyant eiect of the latter on said resistor, and electrical con-V nCtOnS for said conductor and the upper Gnd of said resistor.v

2. Apparatus of the character described comprising a substantially vertical tube, a body of a liquid electrical conductor contained in said tube, a resistor arranged in said tube and projecting downwardly into said conductor, an armature connected to the upperend of said resistor, a solenoid surrounding said tube and adapted to magnetically affect the position of said armature to vary the depth of the immersion of said resistor in said conductor, means carried by said resistor below the level of said conductor for increasing the buoyant effect of the latter on said resistor and said armature, and electrical connections for said conductor and the upper end of said resistor and including said armature.

3. Apparatus of the character described comprising an integral vertical glass tube, a body of a liquid electrical conductor contained in said tube, a moving element in said tube including a lower resistor projecting downwardly into said conductor and an armature connected atits lower end to theupper end of said resistor, a solenoid surrounding said tube and adapted to magnetically affect the position of said armature to vary the depth of the immersion of said resistor in said conductor, an electrical conductor embedded in the bottom of said tube in contact with said liquid conductor, and an electrical conductor embedded in the top of said tube and having a flexible portion electrically connected to said armature.

4. Apparatus constructed in accordance with claim 3 provided with a, displacer surrounding the lower end of said resistor for increasing the buoyant effect of the liquid conductor on said moving element.

5. Apparatus constructed in accordance with claim 3 provided with a knife edged damping disk surrounding the lower portion of said resistor below the level of said liquid conductor to retard vertical movement of said moving element.

6. Apparatus constructed in accordance with claim 3 provided with an annular displacer surrounding the lower end of said moving element for increasing the buoyant `eil'ect of the liquid conductor thereon, and

knife edged damping disks loosely surrounding said moving element above and below said displacer and below the level of the liquid conductor to retard vertical movement of said moving element.

7. Apparatus of the character described comprising a vertical tube sealed at opposite ends, a body of a liquid electrical conductor contained in said tube, a resistor arranged in said tube and projecting downwardly into said conductor, the upper end of said resistor being enlarged in circumference and being provided with an axial opening projecting downwardly to a. point below the level of said conductor when said resistor is in lower position, the interior of said opening being metal plated, an armature secured at its lower end to the upper end of said resistor and provided with a plurality of depending circumferentially arranged resilient ingers extending into said axial opening substantially to the bottom thereof and contacting with said metal plating, aV solenoid surroundin said tube and adapted to magnetically a ect the position of said armature to vary the depth of the immersion of said resistor in said conductor, a non-magnetic conducting rod secured to said armature and projecting upwardly therefrom, and electrical connections for said conductor and the upper end-of said conducting rod.

8. Apparatus of the character described comprising a vertical tube sealed at opposite ends, a solenoid surrounding said tube intermediate its ends, a body of mercury contained in said tube, a. resistor arranged in said tube and projecting downwardly into said conductor, an armature secured at its lower end to the upper end of said resistor and projecting partially through said sole.V

wid, a non-magnetic conducting rod secured at lower end to said armature and projecting upwardly therefrom to a point above said solenoid,. Said conducting rod beingk if.

plated with a metal having substantially no afiinity for mercury, means for guiding said resistor andsaid armature in said tube, and electrical Connections for said conductor and the upper end of said conducting rod.

9( Apparatus constructed in accordance with Claim 8 provided with a bumper carried by the upper end of said conducting rod to resiliently limit the upward movement thereof, .said bumper including a plurality of spaced spring fingers.

1,0. Apparatus constructed in accordance with claim 8 wherein said resistor is pro.k vided at the, lower end thereof with a displacer to increase the buoyant eilect of said liquid Conductor on said resistor, said armature and said conductingrod.

1,1., Apparatusy constructed in accordance.

with claim 8 provided with means arranged` within said tube adjacent opposite endsv thereof for limiting the vertical movement of said resistor, said armature and said conducting rod, said last named means com- Pl'Sng a lower spring carried by said tube and an upper spring member carried by said conducting rod. f

Apparatus of thel character described comprising a vertical tube sealed at opposite ends,l a solenoid surrounding said tube intermediate itsends, a body of a liquid elecf trical .conductor contained in said tube, a

'i tween. 20

resistor arranged in said'tube and projectingdownwardly into said conductor, a cast iron armature secured Yat its lower end to `the upper end of said resistor and projecting partially through said solenoid," a non-mabn'etic conducting rod secured at its lower end in said armature and projecting;r upwardly therefrom 'to a vpoint above said solenoid, said conducting rod being plated with iron, electrical connections for said conductor and the upper end of said conducting rodand means for longitudinally adjusting said tube Awith respect to said solenoid.

13. Apparatusconstructed in accordance with claim 12 provided. with means for spac- Zinn said tube from the interior of said solenoid to permit the passage of air therebe- 14. Apparatus of the character described 'comprising a substantially vertical tube. av

body of avlioguid electrical conductor contained in said tube, a resistor arranged 1n said tube and projectinga downwardly into ,sistorbeing provided with an axial opening` projectingy downwardly to a point below the level of said conductor when said resistor is in lower position, an armature secured to l netically affect the position of said armature v to vary the denthfoi2 immersion of said resistor in saidjconductor, and electrical connections forfsaid conductor and the upner endvof said resistor ture. j

15. Apparatus constructed in accordance with claim 14 wherein the denendine nortion of said armature'is radially slotted to Drovidev a plurality of resilient inpers havingr arcuate outer surfaces contacting with the metal platina of said axial opening.

16. Apparatus oit' the character described comprising a substantially vertical tube, a body of a liouid electr; ll conductor contained in saidtube a resistor arranged in saidtubev and project-ina' downwardly into said'- conductor7 the upperr end of said resistor being' provided with anaxial opening said conductoigthe upper end of said re-V and including 'said'arlna- FRANK wINrHRoP MERRILL.

projecting downwardly to a point below the with4 said resistor, a solenoid surroundingl Asaidltube and adapted to magnetically af- Y feet the position of said armature tof vary iet 

